This invention relates to an oil burner for kerosine stored for a long term (hereinafter referred to as "long-term stored kerosine"), and more particularly to an oil burner for ensuring normal combustion of quality-deteriorated kerosine such as kerosine changed into a macromolecular structure or highly polymerized (hereinafter referred to as "macromolecular kerosine" or "highly-polymerized kerosine") due to prolonged storage thereof, kerosine having deteriorated quality similar to such macromolecular kerosine or the like.
An oil burner of the type of automatically controlling a fuel combustion quantity which has been conventionally known in the art generally includes a burner body for combustion of an oil fuel such as kerosine, a fuel pump for feeding the fuel to the burner body, an air fan for feeding air to the burner body, and a combustion control unit for controlling the fuel pump and air fan to control the quantity of combustion in the burner body. Kerosine used as the fuel in such an oil burner comprises a combination of oil species within a predetermined range collected by distillation, resulting in a molecule of the kerosine being substantially varied in a wide range. Also, so-called carried-over kerosine which was purchased in the preceding year and carried over to the next year, kerosine excessively contacted with oxygen in air while keeping a cap of an oil tank open, kerosine exposed to an elevated temperature or the like is changed into a macromolecular structure or highly polymerized due to oxidation of the kerosine, a change in quality or properties thereof, or the like. Further, a molecular weight of kerosine is varied depending on a country. Thus, there are actually seen countries that often sell kerosine having quality similar to carried-over kerosine or kerosine deteriorated in quality to a degree sufficient to generate tar by combustion due to incorporation of naphtha thereinto. Unfortunately, the conventional oil burner fails to control combustion in view of quality of kerosine used.
Thus, the conventional oil burner, when quality-deteriorated kerosine such as carried-over kerosine which is deteriorated in quality due to high-polymerization is used as a fuel therefor, causes kerosine collected in a vaporization section of the burner body to be partially changed into tar. Unfortunately, the tar thus formed leads to abnormal combustion or a failure in satisfactory combustion such as incomplete combustion.